Bioabsorbable polymeric medical device

ABSTRACT

In embodiments there is described a cardiovascular tube-shaped lockable and expandable bioabsorbable scaffold having a low immunogenicity manufactured from a crystallizable bioabsorbable polymer composition or blend.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Applications Ser.Nos. 60/913,264, filed on Apr. 20, 2007; 60/862,433, filed on Oct. 20,2006; and 60/807,932, filed on Jul. 20, 2006.

The references cited in this specification, and their references, areincorporated by reference herein in their entirety where appropriate forteachings of additional or alternative details, features, and/ortechnical background.

FIELD OF INVENTION

The invention relates to polymeric medical devices for implantation intoluminal structures within the body. In particular, the medical devicecomprises a polymeric structure which polymer is bioabsorbable,biocompatible and structurally configured to fit within luminalstructures such as blood vessels in the body. The medical device isuseful for treating diseases such as atherosclerosis, restenosis andother types of cannalicular obstructions.

BACKGROUND

Disclosed in embodiments herein is a novel medical device, for example,a cardiovascular tube-shaped expandable scaffold having a meanderingstructural entity or plurality thereof Such novel medical device mayinclude a locking mechanism at its end for securing the device in acrimped position onto a carrier means for deployment. The lockingmechanism provides structural means for securing the crimped scaffoldonto a carrier module so as to remain in an immobilized position duringinsertion and delivery to the treatment target area. The locked-inrestraint of the scaffold can be maintained until implantation of thedevice or unless it is overcome by expansion means of the carriermodule.

A persistent problem associated with the use of metallic stenting totreat, for example, vascular occlusion is found in the formation of scartissue surrounding the device upon insertion of the device at the siteof blood vessel injury, the so-called process of restenosis. Many haveconcluded that there is a continued risk of stent thrombosis due to thepermanent aspect of metallic stents in the blood vessel, either alone orcontaining a drug coating composition, which therapy was intended toprevent such calamities. Moreover, metallic or non-absorbable polymericstents may prevent vascular lumen remodeling and expansion.

It is known that any injury to body tissue or organ undergoes a woundhealing process involving, for example, collagen type 1 synthesis and inparticular, smooth muscle cell migration in particular from bloodvessels, which result in concomitant hardening of the healed area andre-narrowing of the blood vessel diameter. Therefore, an invasiveprocedure to surgically implant a medical device, such as a stent into ablood vessel, should require a scaffold of enough plasticity to preventvessel wall contusion or blood capillary injury during scaffoldexpansion and placement within the area of treatment.

Another long-term goal for avoiding restenosis is applying a surgicalprocedure with a medical device with none or substantially lowimmunogenicity

The continued risk of stent thrombosis due to the permanency of metallicstents after implantation has not been overcome by coating of themetallic structures with drug compositions intended to prevent suchproblems. On the contrary, the death rate from these coatings has beenprohibitive. Moreover, metallic or polymeric non-absorbable stents mayprevent vascular lumen remodeling and expansion. Numerous approacheshave been tried to prevent or heal tissue and reduce complementactivation of the immune response or platelet aggregation. Furthermore,there is a need to eliminate or reduced an inflammatory response at thesite of implantation, and lower potential for trauma upon break-up of animplant and/or its component materials. A most desirable improvementtarget may be found in the need for increased flexibility of shape andstructure of medical devices for implantation, particularly into bloodvessels.

REFERENCES

Reference is made to U.S. Pat. No. 6,607,548 B2 (Inion), issued Aug. 19,2003, which discloses compositions of biocompatible and bioresorbablematerials using a lactic acid or glycolic acid based polymer orcopolymer blends with one or more copolymer additives. The referencediscloses that implants made from these materials are cold-bendablewithout crazing or cracking. EP 0401844 discloses a blend ofpoly-L-lactide with poly-D-DL-lactide. U.S. Pat. No. 6,001,395 disclosesdrug delivery with lamellar particles of a biodegradable poly(L-lactide)or copolymers or blends thereof, being at least in part crystalline.U.S. Pat. No. 7,070,607 discloses an aneurysm repair coil comprising abioabsorbable polymeric material carrying an embolic agent whereinthrombogenicity is controlled by the polymer composition.

SUMMARY

Among other things, the present inventors have recognized a need forimproved implant configuration, including scaffold/stent configurationsfor in vivo application. The inventors have also recognized a need todevelop a compatible polymer blend for implants, such as stents andvascular synthetic grafts, which provide a toughening mechanism to thebase polymer when the medical device is deployed in the body. They havehypothesized that the later may be performed by imparting additionalmolecular free volume to the base polymer to encourage sufficientmolecular motion to allow for re-crystallization to occur atphysiological conditions especially when additional molecular strain isimparted to the implant. They have theorized that increased molecularfree volume can also increase the rate of water uptake adding both aplasticizing effect as well as increasing the bulk degradation kinetics.

For example, the medical device could comprise a polymer with low immunerejection properties such as a bioabsorbable polymer composition orblend, having a combination of mechanical properties balancingelasticity, rigidity and flexibility. The polymer composition couldproduce a low antigenicity by means of a biocompatible base material,such as, without limitaton, a bioabsorbable polymer, copolymer, orterpolymer, and a copolymer or terpolymer additive. These kinds ofpolymer structures may advantageously undergo enzymatic degradation andabsorption within the body. In particular, the novel composition mayallow for a “soft” breakdown mechanism that is so gradual that thebreakdown products or polymer components are less injurious to thesurrounding tissue and thus reduce restenotic reactions or inhibitrestenosis entirely.

The present inventors have also proposed novel designs which may employsuch bioabsorbable, biocompatible and biodegradable material to makeadvantageous scaffolds, which may afford a flexibility andstretchability very suitable for implantation in the pulsatilemovements, contractions and relaxations of, for example, thecardiovascular system.

Embodiments disclosed herein include, medical devices such as stents,synthetic grafts and catheters, which may or may not comprise abioabsorbable polymer composition for implantation into a patient.

In one embodiment, a cardiovascular tube-shaped expandable scaffold suchas a stent is provided, having a low rejection or immunogenic effectafter implantation, which is fabricated from a bioabsorbable polymercomposition or blend having a combination of mechanical propertiesbalancing elasticity, rigidity and flexibility, which properties allowbending and crimping of the scaffold tube onto an expandable deliverysystem for vascular implantation. The instant devices can be used in thetreatment of, for example, vascular disease such as atherosclerosis andrestenosis, and can be provided in a crimpable and/or expandablestructure, which can be used in conjunction with balloon angioplasty.

In an embodiment, the medical device can be provided as an expandablescaffold, comprising a plurality of meandering strut elements orstructures forming a consistent pattern, such as ring-like structuresalong the circumference of the device in repeat patterns (e.g., withrespect to a stent, without limitation, throughout the structure, at theopen ends only, or a combination thereof). The meandering strutstructures can be positioned adjacent to one another and/or inoppositional direction allowing them to expand radially and uniformlythroughout the length of the expandable scaffold along a longitudinalaxis of the device. In one embodiment, the expandable scaffold cancomprise specific patterns such as a lattice structure, dual-helixstructures with uniform scaffolding with optionally side branching.

In one embodiment, a bioabsorbable and flexible scaffold circumferentialabout a longitudinal axis so as to form a tube, the tube having aproximal open end and a distal open end, and being expandable from anunexpanded structure to an expanded form, and being crimpable, thescaffold having a patterned shape in expanded form comprising:

-   -   a) a plurality of first meandering strut patterns, each of the        first meandering strut pattern being interconnected to one        another to form an interconnected mesh pattern circumferential        about the longitudinal axis; and    -   b) at least two second strut patterns nested within the        interconnected mesh pattern, each of said second strut patterns        comprising a hoop circumferential about the longitudinal axis,        said hoop having an inner surface proximal to the longitudinal        axis and an outer surface distal to the longitudinal axis, the        hoop inner and outer surfaces about their circumferences being        orthogonal to the longitudinal axis and within substantially the        same plane.

In one embodiment, the first meandering strut patterns can be generallyparallel to said longitudinal axis, generally diagonal to saidlongitudinal axis, generally orthogonal to said longitudinal axis, orgenerally concentric about said longitudinal axis. The second strutpatterns can be made of a material, which substantially crystallizeswhen said tube is in its expanded state, but does not substantiallycrystallize in its unexpanded state. The second strut patterns caninclude at least one hoop having a through-void, wherein saidthrough-void is configured to permit the radius of said at least onehoop to be expanded when said at least one hoop is subject to anexpanding force which exceeds its nominal expanded state but does notresult in hoop failure.

In one embodiment, each of the first meandering strut patterns of thescaffold is essentially sinusoidal, and each of the second strutpatterns is substantially non-sinusoidal. The first meandering strutpatterns of a scaffold can extend from the proximal open end to thedistal open end of the tube. In another embodiment, each of the secondstrut patterns can be found at the proximal open end and the distal openend. In one embodiment, each of the second strut patterns is furtherfound between the proximal open end and the distal open end.

In one embodiment, the scaffold can comprise a structure wherein each ofthe second strut patterns can be found between the proximal open end andthe distal open end but not at the proximal open end or distal open end.In another embodiment, the scaffold can comprise a structure wherein thesecond strut patterns can be found at at least one of the proximal openend or the distal open end.

In a specific embodiment, the scaffold comprises a stent having anunexpanded configuration and an expanded configuration; an outer tubularsurface and an inner tubular surface, the stent comprising: a pluralityof biodegradable, paired, separate circumferential bands having apattern of distinct undulations in an unexpanded configuration andsubstantially no undulations in an expanded configuration, theundulations of the biodegradable, paired, separate circumferential bandsin the stent in an unexpanded state being incorporated into asubstantially planar ring in an expanded state, and a plurality ofbiodegradable interconnection structures spanning between each pair ofcircumferential bands and connected to multiple points on each band ofthe paired bands.

In an embodiment, the stent interconnecting structures comprise apattern of undulations both in an unexpanded and expanded configuration.In an alternate embodiment, the interconnection structures comprise apattern containing no undulations in both an unexpanded and expandedconfiguration. The interconnection structures of the stent can expandbetween undulations of paired circumferential bands.

In one embodiment, at least one of the plurality of paired biodegradablecircumferential bands includes along its outer tubular surface, aradio-opaque material capable of being detectable by radiography, MRI orspiral CT technology. Alternatively, at least one of the interconnectionstructures includes a radio-opaque material along its outer tubularsurface, which can be detectable by radiography, MRI or spiral CTtechnology. The radio-opaque material can be housed in a recess on oneof the circumferential bands, or in a recess on one of theinterconnection structures. In one embodiment, at least one of theinterconnection structures and at least one of the circumferential bandsincludes a radio-opaque material along the outer tubular surface, whichis detectable by radiography, MRI or spiral CT technology.

In another embodiment, a biosorbable and flexible scaffoldcircumferential about a longitudinal axis and substantially forming atube, the tube having a proximal open end and a distal open end, andbeing crimpable and expandable, and comprising in expanded form: a) atleast two rings circumferential about the longitudinal axis, the ringshaving an inner surface proximal to the longitudinal axis, an outersurface distal to the longitudinal axis, a top surface proximal to theproximal open end and a bottom surface proximal to the distal open end,the ring inner and outer surfaces about their circumferences beingorthogonal to the longitudinal axis and within substantially the sameplane, and b) a plurality of meandering strut patterns located betweenthe at least two rings and circumferential coursing about thelongitudinal axis; the plurality of meandering strut patterns connectedto the rings at at least two connection points on the circumference ofeach ring, and each connection point on the circumference of the ring onboth the top ring surface and the bottom ring surface; wherein each ofthe connection points with any particular ring is symmetrical instructure above and below the upper and lower surface of the ring.

In one embodiment, the scaffold comprises a structure wherein theconnection points of the rings, the meandering strut patterns above thering upper surface and below the ring lower surface in conjunction forma stylized, letter H configuration. In another embodiment, the scaffoldcan comprise a structure wherein at the connection points of the rings,the meandering strut patterns above the ring upper surface and below thering lower surface in conjunction form two abutting sinusoids. In analternate embodiment, the scaffold can comprise a structure wherein atthe connection points of the rings, the meandering strut patterns abovethe ring upper surface and below the ring lower surface in conjunctionform two sinusoids with intervening structure connecting the same andthe ring. In one embodiment, the connection points of the rings havebetween 2 through 6 meandering strut pattern connections at eachconnection.

In another embodiment, an expandable biodegradable tubular scaffoldcomprising a plurality of biodegradable first meanders forming aninterconnected mesh. The mesh extending circumferentially about alongitudinal axis; wherein each of the biodegradable first meanders aremanufactured from a racemic polymer which crystallizes under the strainof expansion of the tubular scaffold, and also comprising a plurality ofbiodegradable second meanders, each of the second meanders beingseparate from another, and each extending circumferentially about thelongitudinal axis in a single plane, the second meanders being nestedin, and interconnected to, the first meanders. In this embodiment, thescaffold's first meanders are generally parallel to the longitudinalaxis, generally diagonal to the longitudinal axis, generally orthogonalto the longitudinal axis, or are concentric about the longitudinal axis.The second meanders are made from a material which crystallizes when thetube is in its expanded state, but does not substantially crystallize inits unexpanded state, and at least one of the second meanders includesat least one through-void, which is configured to permit stretching ofthe second member without failure of the member.

In one embodiment, the first meanders form a strut pattern that issinusoidal when the tube is in an expanded form, the second meandersform a strut pattern that is substantially non-sinusoidal when the tubeis in an expanded form. In this and other embodiments, the firstmeanders form a strut pattern that extends from the proximal open end tothe distal open end of the tube, and the second meanders form a strutpattern that is found at the proximal open end and the distal open end.The second meanders can also form a strut pattern that is further foundbetween the proximal open end and the distal open end, or the secondmeanders form a pattern that is found between the proximal open end andthe distal open end but not at the proximal open end or the distal openend.

In an alternate embodiment, a method for fabricating a tube-shapedscaffold comprising: preparing a racemic poly-lactide mixture;fabricating a biodegradable polymer tube of the racemic poly-lactidemixture; laser cutting the tube until such scaffold is formed. In thisembodiment, the fabrication of the scaffold can be performed using amolding technique, which is substantially solvent-free, or an extrusiontechnique.

There is also provided a method for fabricating the tube-shaped scaffoldcomprising, blending a polymer composition comprising a crystallizablecomposition comprising a base polymer of poly L-lactide or polyD-lactide linked with modifying copolymers comprising poly L(orD)-lactide-co-tri-methylene-carbonate or poly L(orD)-lactide-co-e-caprolactone in the form of block copolymers or asblocky random copolymers wherein the lactide chain length issufficiently long enough to allow cross-moiety crystallization; moldingthe polymer composition to structurally configure the scaffold; andcutting the scaffold to form the desired scaffold patterns. In thisembodiment, the blended composition comprises a recemic misture of polyL-lactide and poly-D lactide. Accordingly, medical devices such as astent, produced by this method consist essentially of a racemic mixtureof a poly-L and poly-D lactide. In this embodiment, the stent cancomprise other polymer materials such as trimethylcarbonate. Inembodiment wherein the device comprises trimethylcarbonate, the amountof trimethylcarbonate does not exceed more than 40% of the weight of thestent.

In another embodiment, an expandable tube-shaped scaffold having aproximal end and a distal end defined about a longitudinal axis isprovided. The scaffold comprising: (a) a plurality of first meanderingstrut elements interconnected with one another at least one point insuch a manner to form a circumferential tube-shaped structure, the firstmeandering strut elements forming a tubular mesh which is crimpable andexpandable; (b) a second meandering strut element which is operativelyconfigured to be crimpable and expandable and configured to form ahoop-shaped strut of the scaffold after expansion; and (c) a lockingmeans permitting the scaffold to be locked in a crimped position;wherein the scaffold comprises a expansion crystallizable, bioabsorbableracemate polymer composition or blend.

In one lock embodiment, the tube-shaped scaffold can comprise astructure wherein the locking means is a two-part portion of one ordifferent meandering strut elements located at or near both the proximaland distal ends of the tube-shaped scaffold. In this embodiment, thetwo-part portion of the locking means can entail, for example, asnap-fit engagement in the crimped position of the scaffold, wherein thelocking means is disengaged by scaffold expansion. In alternateembodiments, the tube-shaped scaffold can comprise a locking meanscomprising a snap-fit key-in-lock configuration wherein the designresembles a dovetail type interlocking means. The tube-shaped scaffoldcan also comprise locking means comprising a snap-fit key-in-lockconfiguration resembling a ball-joint type interlocking means; acantilever arm hooking an oppositely shaped end piece of the plasticscaffold, and the like.

The tube-shaped scaffold can be mounted or carried on a expandableballoon carrier device and can be sized to stretch from a crimped tubediameter to a diameter sufficient for implantation inside the lumen of avascular system.

In another embodiment, the expandable scaffold comprises a set ofinterlocking meandering struts stabilizing the implanted scaffold in anexpanded or implanted configuration, wherein the scaffold polymerundergoes a molecular reorientation and crystallization during theradial strain of expansion. The scaffold can vary from a cylindrical toa conal shape or combination thereof. In the embodiments describedherein, the scaffold's biodegradable polymer displays breakdown kineticssufficiently slow to avoid tissue overload or other inflammatoryreactions. The polymer core material comprising at least oneencapsulated drug for localized treatment of the vascular wall andlumen.

The tube-shaped scaffold can also comprise one or more than onepharmaceutical substances, which can be encapsulated within thepolymeric structure for release of the drugs locally and for thetreatment and prevention of tissue inflammation and plateletaggregation. The tube-shaped scaffold can also comprise at least oneattached or embedded identification marker, which can be attached orembedded identification marker comprising a spot radioopacity or adiffuse radioopacity.

The tube-shaped scaffold can also comprise meandering struts which canbe interlocked by means of ringlet connectors comprising configurationsselected from one or more of the groups consisting of: shaped-like an H,shaped-like an X, perforated circle, double adjacent H, triple adherentconnection, two adjacent parallel connections, sinusoidal connect ofparallel struts.

In another embodiment, a bioabsorbable and flexible scaffoldcircumferential about a longitudinal axis so as to form a tube, the tubehaving a proximal open end and a distal open end, and being crimpableand expandable, comprising (a) a plurality of first meandering strutelements interconnected with one another at least points in such amanner to form a circumferential tube-shaped structure, the firstmeandering strut elements forming a tubular mesh which is crimpable andexpandable; (b) a second meandering strut element which is operativelyconfigured to be crimpable and expandable and configured to form ahoop-shaped strut of the scaffold after expansion the hooped-shapedstrut having a inner surface proximal to the longitudinal axis, an outersurface distal to the longitudinal axis, a top surface proximal to theproximal open end and a bottom surface proximal to the distal open end;the second meandering strut element interconnected the plurality offirst meandering strut elements; and (c) at least a pair of lockingstructures located proximal to either of the inner surface or the outersurface of the second meandering strut element, the pair of lockingstructures being configured to operatively lock to one another when thescaffold is in an unexpanded state, but to separate from one anotherwhen the scaffold is in an expanded state.

The scaffold can comprise locking structures comprising a pair ofcantilevered arms that interconnect with one another when the scaffoldis in an unexpanded state; locking structures comprising opposing maleand female connectors; locking structures comprising connectors adjoinedto one another with a friable connection when the scaffold is in anunexpanded state, but separate connectors when the friable connection isbroken when the scaffold is in an expanded state; locking structurescomprising a dovetail-type interlocking connectors; locking structurescomprising a cantilevered arm and a portion of the a second meanderingstrut element when the scaffold is in an unexpanded state, and form acantilevered arm extending from, and a recess in, the second meanderingstrut element when the scaffold is in an unexpanded state. The lockingstructures can be configured and positioned with respect to such tube toallow for locking of an unexpanded state, and when carried on aexpandable balloon carrier device.

In another embodiment, a crimpable bioabsorbable and flexible scaffoldcircumferential about a longitudinal axis so as to form a tube, the tubehaving a proximal open end and a distal open end, and being expandablefrom an unexpanded to an expanded form, and containing locking structureto lock one component of the scaffold to another, the scaffold having apatterned shape in expanded form comprising, (a) a plurality of firstmeandering strut patterns, each of the first meandering strut patternbeing interconnected to one another to form an interconnected meshpattern circumferential about the longitudinal axis; and (b) at leasttwo second strut patterns nested within the interconnected mesh pattern,each of the second strut patterns comprising a hoop circumferentialabout the longitudinal axis, the hoop having an inner surface proximalto the longitudinal axis and an outer surface distal to the longitudinalaxis, the hoop inner and outer surfaces about their circumferences beingorthogonal to the longitudinal axis and within substantially the sameplane.

The expandable tubular scaffold comprises one or more of the firstmeanders include receptacle structure for lock-fit reception ofcorresponding lock structure. The expandable tubular scaffold comprisesa structure wherein the corresponding locking structure is part of theone or more of first meanders, which incorporate thereon receptaclestructure, and the corresponding locking structure is locked withrespect to the receptacle structure. In one embodiment, the expandabletubular scaffold also comprises one or more of the second meandersincludes receptacle structure for lock-fit reception of correspondinglock structure, which further includes the corresponding lockingstructure, and the corresponding locking structure is locked withrespect to the receptacle structure. In one embodiment, the expandabletubular comprises a structure wherein one or more of the first meandersincludes receptacle structure for lock-fit reception of correspondinglock structure.

In another embodiment, the expandable tubular scaffold comprises astructure wherein one or more of the second meanders includescorresponding lock structure for the receptacle structure, and thecorresponding locking structure is locked with respect to the receptaclestructure; or one or more of the second meanders includes receptaclestructure for lock-fit reception of corresponding lock structure.

In an alternate embodiment, the expandable tubular scaffold comprises astructure wherein one or more of the first meanders includes thecorresponding lock structure, the corresponding locking structure islocked with respect to the receptacle structure.

In another embodiment, a biosorbable and flexible scaffoldcircumferential about a longitudinal axis so as to form a tube, the tubehaving a proximal open end and a distal open end, and being crimpableand expandable, and having a patterned shape in expanded formcomprising, a first multicomponent strut pattern helically coursing fromthe proximal open end to the distal open end of the tube; a secondmulticomponent strut pattern helically coursing from the proximal openend to the distal open end of the tube; wherein a component of the firstmulticomponent strut pattern opposes by from about 120° to about 180° acomponent of the second multicomponent strut pattern as each helicallycourses from the proximal open end to the distal open end of the tube.In one embodiment, the scaffold comprises a structure wherein eachcomponent strut pattern of the first multicomponent strut pattern issubstantially the same in configuration. The scaffold can also comprisea structure wherein each component strut pattern of the secondmulticomponent strut pattern is substantially the same in configuration.Alternatively, the scaffold can comprise a structure wherein eachcomponent strut pattern of the first and second multicomponent strutpattern is substantially the same in configuration. In this embodiment,that is, wherein each opposing component of the component strut patternbetween the first multicomponent strut pattern and second multicomponentstrut pattern is substantially the same in configuration; and can forman stylized letter H configuration; a stylized X configuration; astylized S configuration; a stylized 8 configuration; or a stylized Iconfiguration.

The scaffold can comprise a third multicomponent strut pattern helicallycoursing from the proximal open end to the distal open end of the tube.The scaffold can further comprise a fourth multicomponent strut patternhelically coursing from the proximal open end to the distal open end ofthe tube, and a fifth multicomponent strut pattern helically coursingfrom the proximal open end to the distal open end of the tube. Eachhelix of a pair of the multicomponent strut patterns may turn about thetube in a left-handed screw direction. Alternatively, the scaffold cancomprise a structure wherein each helix of both of the multicomponentstrut patterns turns about the tube in a right-handed screw direction.In a further embodiment, at least one helix of both of themulticomponent strut patterns turns about the tube in a left-handedscrew direction while another helix turns in a right-handed screwdirection. In yet another embodiment, all of the helices of themulticomponent strut patterns turns about the tube in the same-handeddirection.

In another embodiment, there is disclosed a biosorbable stent having aplurality of helically coursing multicomponent strut patterns from theproximal open end to the distal open end of the tube wherein a componentof each the multicomponent strut pattern opposes by from about 120° toabout 180° another component of another multicomponent strut pattern aseach helically courses from the proximal open end to the distal open endof the tube. In this embodiment, each helix of the multicomponent strutpatterns turns about the stent in a left-handed screw direction; eachhelix of both of the multicomponent strut patterns may turn about thestent in a right-handed screw direction. Alternatively, the scaffold cancomprise helices wherein at least one helix of the multicomponent strutpatterns turns in a left-handed screw direction while another helixturns about the stent in a right-handed screw direction; or wherein allof the helices of the multicomponent strut patterns turns about thestent in the same handed direction.

There is also provided, a flexible scaffold circumferential about alongitudinal axis so as to form a tube, the tube having a proximal openend and a distal open end, and being crimpable and expandable, andhaving a patterned shape in unexpanded form comprising; a firstsinusoidal strut pattern comprising a series of repeated sinusoidsdefined by an apex section and a trough section, the repeated sinusoidscoursing from the proximal open end to the distal open end of the tube;and a second sinusoidal strut pattern comprising a series of repeatedsinusoids defined by an apex section and a trough section, the sinusoidsof the second sinusoidal strut pattern being about 180° out of phase towith respect to the apex and the troughs of the first sinusoidal strutpattern; wherein the second sinusoidal strut pattern is connect to thefirst sinusoidal strut pattern at at least two points, and wherein theconnection at the points is from an apex of a sinusoid of the firstsinusoidal pattern to an apex of a sinusoid of the second sinusoidalpattern.

In one embodiment, the scaffold can comprise a structure wherein thefirst sinusoidal strut pattern and the second sinusoidal strut patternare repeated multiple times, one after the other to form the scaffold;or wherein the first sinusoidal strut pattern and the second sinusoidalstrut pattern are the same; or wherein the first sinusoidal strutpattern and the second sinusoidal strut pattern are different. Thescaffold can be made of a biodegradable material, such as poly-lactide.In this embodiment, the scaffold comprises a structure wherein thesecond sinusoidal strut pattern is connected to the first sinusoidalstrut pattern at at least three or four points.

In another embodiment, a biosorbable and flexible scaffoldcircumferential about a longitudinal axis so as to for a tube, the tubehaving a proximal open end and a distal open end, and being crimpableand expandable, and having a patterned shape in unexpanded formcomprising; a first sinusoidal strut pattern comprising a series ofrepeated sinusoids defined by an apex section and a trough section, therepeated sinusoids coursing from the proximal open end to the distalopen end of the tube; a second sinusoidal strut pattern comprising aseries of repeated sinusoids defined by an apex section and a troughsection, the sinusoids of the second sinusoidal strut pattern being inphase with respect to the apex and the troughs of the first sinusoidalstrut pattern; wherein the second sinusoidal strut pattern is connectedto the first sinusoidal strut pattern at at least two points, andwherein the connection at the points is from an apex of a sinusoid ofthe first sinusoidal pattern to an apex of a sinusoid of the secondsinusoidal pattern.

In this embodiment, the first sinusoidal strut pattern and the secondsinusoidal strut pattern are repeated multiple times, one after theother form the scaffold; the first sinusoidal strut pattern and thesecond sinusoidal strut pattern are the same or different. The scaffoldis made of a biodegradable material, such as a polymer such as apoly-lactide polymer; and comprises a structure wherein the secondsinusoidal strut pattern is connected to the first sinusoidal strutpattern at at least three or four points.

In an embodiment wherein the tubular-shaped structure is a stent, thestent comprises a plurality of sinusoidal-like or meandering strutpatterns encompassing the diameter of the tubular structure, whereineach sinusoidal ring-like structure can be continuous with an adjacentsinusoidal ring-like structure at a point. Adjacentsinusoidal/meandering patterns can be continuous at at least one point.In one embodiment, the stent scaffold can be formed by two differenttypes of meandering elements, the first meandering element comprises azig-zag pattern/sinusoidal-like structure comprising with peaks andvalleys which can extend the entire circumference of the scaffold, sothat the meandering element can maintain a sinusoidal shape even whenthe scaffold structure is in its fully expanded configuration. A secondtype of meandering element also forms the stent scaffold, and can beintercalated or positioned in between adjacent first meanderingelements, so that when the scaffold structure is fully deployed, thesecond type of meandering element forms a ring-like or hoop structurewhich can adapt to fully fit the diameter of a tubular organ space wherethe scaffold is deployed. The ring-like (also referred to as ringlet)element provides the tubular scaffold with increased hoop strength andcan prevent collapsing of the scaffold once deployed. More specifically,this embodiment provides the ring, or hoop its expanded state, at leastat one end of the tubular device for securing or anchoring the scaffoldposition in the organ space. In addition, another embodiment can provideat least one other ring or ringlet nestled within the scaffold so as toprevent dislocation of the scaffold from its implanted position. Theembodiment can also provide a plurality of ringlets distributed randomlyor in a regularly spaced pattern along the length of the scaffold. Inthe case of an expanded scaffold, the ringlets are designed to expandutmost into a ring or hoop shape or expand to a degree so as to retainsome sinusoidal shape for more flexible, less rigid structuralcharacteristics. The presence of secondary meandering struts both in thehoop shape at a scaffold end or anywhere along the scaffold axis, aidsin preventing scaffold “creep” by tightly pushing against the wall ofthe organ space, as e.g. cardiovascularity. “Creep” in the presentinvention is defined as gradual dislocation of an implant from theoriginal emplacement in the organ space. This change as caused bypulsating organ walls as well as bodily fluid flux, can be countered byre-crystallized hoop or ring entities that span the luminal space, presstightly against the surrounding tissue and yet exhibit enough elasticityand compatibility to reduce local injurious impact.

Embodiment devices may be comprised of a polymeric composition that isdesigned to be flexible in the unexpanded state and to be increasinglyrigid and strong in proportion to its expansion. More specifically, thepreferred embodiment is designed such that the end ring deriving fromthe secondary less meandering strut element would stretch to a hoopconformation at which the scaffold polymer acquires the strengthnecessary to resist compression for advantageous anchorage in the organimplant space. The basis for this differential scaffold strength isfound in the polymer composition which shows an amorphous matrix in therelaxed or crimped configuration but upon cold straining, expanding, orstretching it induces a realignment of the polymeric matrix concomitantwith an increased crystallization resulting in a proportionally enhancedscaffold mechanical strength.

In one embodiment, the tubular scaffold can comprise one or more thanone of a second type of meandering elements and can be positioned in thetubular scaffold at alternating patterns between a first type ofmeandering elements to form a repeat pattern depending of the desiredlength of the tubular scaffold. In another embodiment, there is provideda scaffold configuration comprising meandering strut elements connectedto an expansion-stabilizing ring-shaped portion and a snap-fit lockingmeans operatively configured for securing the scaffold in a crimpedposition on a carrier device.

In one embodiment, a tubular scaffold can be provided in a crimpable andexpandable structure for use in conjunction with balloon angioplasty.Such tubular embodiment optionally may comprise a securing mechanism,which can be positioned at or near the ends of the tubularstructure/scaffold. In this embodiment, the securing mechanism can be ofdifferent designs and structurally configured to secure the flexibleplastic scaffold onto a carrier portion of the delivery system, andwherein the scaffold can be crimped down in a locked position so as tokeep the scaffold immobilized on the carrier for vascular implantation.The securing mechanism may comprise, for example, mechanical lockingmeans, such as snaps, hooks, lock- and key-like structures, matingstructures and abutting structures, and the like, which can engage oneanother and secure the scaffold on the carrier in a tightly crimpedconfiguration. The securing mechanism can prevent dislodging of thescaffold during deployment or transport on a carrier for implantation.For example, the locking means may be structurally configured tooperate, for example, as a snap-fit locking means and can be positionedat or near one end, or at or near both ends of the scaffold. Thesnap-fit locking means may be in the form of a finger-like extension toslide over an adjacent similarly curved scaffold portion positioned inor near the end portion of the tube-like configuration. In oneembodiment of the scaffold that is lockable in the crimped downtransport position includes a snap-fit key-in-lock design similar to adovetail slotting structure.

In another embodiment, the scaffold can be lockable in the crimped downtransport position, by securing means including, a snap-fit, key-in-lockdesign similar to a ball and socket-like joint structure. In anotherembodiment, there is provided a snap-fit, key-in-lock configurationwherein a series of hook-like strut extensions on a meandering ringstructure can interlock with an adjacent oppositely arranged hook-likestrut. In other embodiments, the locking mechanism may comprise frictionenhancing components and other slide interfering properties may be usedto lock in the crimped scaffolding. Thus, in this embodiment, themechanical interlocking features of the crimped scaffold may be enhancedby frictional properties incorporated in the plastic composition. Thesefrictionally enhancing properties may be added to the composition itselfor grafted in the form of a layer or in isolated or stippled surfacecomponents. Suitable agents include ionic or non-ionic substances.Nonionic interactions or weak force attractions play a role enhancingthe frictional component of the scaffold. Ionic additives are preferablyconcentrated on the locking surfaces of the crimped scaffold in solubleform so as to avoid unwanted plasma protein reactions.

In certain embodiments, the locking means of a deployed scaffold can bedisengaged by the expanding means of the delivery carrier. Depending ontheir location, the locking features of the scaffold can be selected tounlock for expansion at different rates from a narrowly crimped deliveryconformation of the entire scaffold structure to a lumen diametersufficient for implantation onto the vascular wall. In one embodiment,the scaffold can be manipulated to vary from a uniform cylindrical to amore conal shape structure allowing for easy of implant installation,relocation and adjustment. For example, the scaffold implant may in aconfiguration comprise a balloon type reversible inflation or dilationmeans which carries the locked scaffold configuration into the body anddeposits the same in the target area by expanding the crimp-lockedscaffold so as to break the locked-in position and stretching theholding ring to a hoop-like form and firmly engage the lumen perimeter.The balloon inflating means comprises a means for heating and/or coolingthe device.

A medical device embodiment, such as a stent, may be manufactured frompolymeric materials which comprises a polymer having breakdown moietiesthat are “friendly” at contact with bodily tissues and fluids such asthe vascular wall. In a specific embodiment, the medical devicecomprises a polymer with breakdown kinetics sufficiently slow to avoidtissue overload or inflammatory reactions which can lead to restenosis,for example, which provides a minimum of 30-day retention of clinicallysupportive strength. In one embodiment the medical device may be enduredin place as much as 3-4 months post-implantation without undergoingsubstantial bioabsorption.

In one embodiment, the implant can undergo transitional change afterimplantation, from a solid flexible implant at implantation, to a“rubbery state” post-implantation which exhibits flexibility, yet enoughresilience and cohesion so as to permit surgical intervention.

In one embodiment, the polymer selected for making the device hasflexibility and elasticity suitable for an implant in friction-freecontact with vascular walls during the cardiovascular pulsingcontractions and relaxations. In an embodiment, the medical devicecomprises a stretchable and elastic scaffold, which has a sufficientlyrigid strength to be capable of withstanding the fluctuatingcardiovascular pressures within a blood vessel. For example, the polymerselection can be based on evaluation criteria based on mass loss interms of decreased molecular weight, retention of mechanical properties,and tissue reaction.

In an embodiment, the implant is manufactured of a bioabsorbable polymerwherein the molecular moieties of the bioabsorbable polymer is composedof a poly L-lactide or a poly D-lactide as the base polymer, whereinmodifying copolymers include poly L(orD)-lactide-co-tri-methylene-carbonate or poly L(orD)-lactide-co-e-caprolactone are used to link the base polymers. Thesecopolymers can be synthesized as block copolymers or as “blocky” randomcopolymers wherein the lactide chain length is sufficiently long enoughto crystallize.

In another embodiment, the composition comprises a base copolymerwherein one moiety is sufficiently long enough and not stericallyhindered to crystallize, such as L-lactide or D-lactide with a lessermoiety, for example Glycolide or Polyethylene Glycol (PEG) ormonomethoxy-terminated PEG (PEG-MME).

In another embodiment, the compositions in addition to the base polymer,the modifying polymer or co-polymer may also have enhanced degradationkinetics such as with an ε-caprolactone copolymer moiety where theε-caprolactone remains amorphous with resulting segments moresusceptible to hydrolysis.

In another embodiment, the composition can incorporate polyethyleneglycol (PEG) copolymers, for example either AB diblock or ABA triblockwith the PEG moiety being approximately 1%. In this embodiment, themechanical properties of the Lactide (see Enderlie and Buchholz SFB May2006) are maintained. In this embodiment the incorporation of either PEGor PEG-MME copolymers may also be used to facilitate drug attachment tothe polymer, for example in conjunction with a drug eluding medicaldevice.

In another embodiment, the medical device comprises a polymeric scaffoldcomprising a base polymer comprising a combination of polymers of lowPEG content of less than 5% in high MW, i.e. 2-3 IV copolymers, whichenables the lactide block to crystallize and impart equivalent strengthto the base polymer.

In an embodiment, the polymer composition allows polymer realignment andthe development of a crystalline morphology. Plastic deformation impartscrystallinity to polymer molecules. A polymer in crystalline state isstronger than its amorphous counterpart. In stent embodiments comprisingring-like structures, the ring-like structures or ringlet may be amaterial state that is inherently stronger than that of a sinusoidalstent segment. that can enhance the mechanical properties of the medicaldevice, enhance processing conditions, and provide potential ofcross-moiety crystallization, for example, thermal cross-links.

Further embodiments disclosed herein include shortening the degradationtime of the polymer in the composition, for example, a medical devicecomprises a bioabsorbable polymer with enhance degradation kinetics. Inthis embodiment the starting material can be a lower molecular weightcomposition and/or a base polymer that is more hydrophilic or liable tohydrolytic chain scission can be employed.

In another device embodiment, the medical device comprises a polymerblend comprising a marker molecule, for example, radio-opaque substance,a fluorescent substance or a luminescent substance, which can serve todetect or identify the medical device once implanted into a patient. Forexample, compounds that can be used as marker molecules include, iodine,phosphorous, fluorophores, and the like. A medical device such as oneemploying fluoroscopy, X-rays, MRI, CT technology and the like may beused to detect the radioopaque substance.

In this and other embodiments of the invention, the medical device cancomprise fillers and one or more pharmaceutical substances for localdelivery. The medical device may, for example, comprise, a biologicalagent, a pharmaceutical agent, e.g. an encapsulated drug (which may beused for localized delivery and treatment—for example, of vascular walltissue and lumen).

In another embodiment, there is provided a scaffold structure comprisinga core degradation schedule which provides more specifically asimultaneously slow release of medication for the treatment andprevention of tissue inflammation and platelet aggregation. The polymercomposition or blend provides uniform degradation in situ avoidingpolymer release in large chunks or particles.

In another embodiment, the polymer compositions are used to manufacturemedical device for implantation into a patient. The medical devicescomprise scaffolds having biodegradable, bioabsorbable and nontoxicproperties and include, but are not limited to stents, stent grafts,vascular synthetic grafts, catheters, vascular shunts, valves and thelike. Biocompatible and bioabsorbable scaffolds may be particularlyfound useful in treatment of coronary arteries. For example, a scaffoldstructure may be manufactured or extruded from a composition comprisinga base polymer material, at least one drug for local delivery and atleast one attached or embedded identification marker.

In another embodiment, a method for treating vascular disease isdisclosed, the method comprising, administering to a person sufferingwith vascular disease a medical scaffold or device comprising astructure made from a biocompatible, bioabsorbable polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures provided herewith depict embodiments that are described asillustrative examples that are not deemed in any way as limiting thepresent invention.

FIG. 1 is a computer simulation illustration depicting a partial view ofan embodiment of a bioabsorbable medical device depicting a scaffoldstrut segments, nested hoop structures, end ring, locking mechanism andinterconnection “H” regions.

FIG. 2 is a computer generated illustration of an embodiment comprisinga bioabsorbable stent design in a somewhat expanded configurationshowing the nested hoop or ring structures, end ring, meandering strutpattern and locking mechanism.

FIG. 3A depicts a computer simulation illustrating a prematurelyexpanded biabsorbable stent scaffold showing an alternating ring or hoopstructures with a meandering strut element pattern and lockingmechanism. FIG. 3B is the same stent scaffold as in FIG. 3A showing aring segment in different states of stress.

FIG. 4A illustrates is a planar view of an embodiment showing abioabsorbable stent scaffold pattern which depicts a planar view of abioabsorbable scaffold featuring repetitive strut pattern in the shapeof an S which can be replaced with other designs as shown. FIG. 4A alsoshows the nested hoop/rings structures. FIG. 4B is an alternateembodiment in a planar configuration which illustrates the nested ringfeatures, wherein the stent strut structure can be replaced with thedesign encompassed at 8. FIG. 4C is a planar view illustration of anembodiment of the invention in which the structural pattern formshelical structures. FIG. 4D illustrates a partial stent structure withhoop or ring structural elements and scaffolding elements in the form asmanufactured. FIG. 4E illustrates the stent structure of FIG. 4D in apartially expanded configuration. FIG. 4F illustrates the stentstructure of FIG. 4D in an expanded configuration.

FIG. 5 depicts an oblique view of a bioabsorbable stent embodimentexhibiting meandering strut segments in a sinusoidal pattern.

FIG. 6A depicts a partial top view of expanded hoop or ring andmeandering or sinusoidal (6B) bioabsorbable strut elements of a stentembodiment. FIG. 6C illustrates a hoop or ring element of abioabsorbable stent showing how radial/transverse load is distributedthrough a ring structure.

FIG. 7A-7C illustrates the polymer fibers alignment in embodiments ofthe bioabsorbable medical devices and how the alignment undergoesplastic deformation upon stress. FIG. 7A illustrates the amorphous stateof the polymer composition for making the devices. FIG. 7B illustratesthe polymer fibers alignment in a partially expanded configuration andFIG. 7C illustrates the crystalline state of the fibers upon expansionof a bioabsorbable stent embodiment.

FIG. 8A illustrates a planar view of a bioabsorbable stent scaffoldembodiment comprising, structural meandering strut elements, nestedhoop/ring elements and having end rings at the openings of the stenttube. FIG. 8B is a planar view of a section of the stent scaffold ofFIG. 8A illustrating the structural meandering strut elements, nestedhoop/ring elements and connection strictures which form the stentscaffold. The stent scaffold is shown in a state as manufacture and alsoshows the nested rings structures in various configurations andconnections between structural meandering elements and hoop elements inthe shape of a stylized letter H configuration. FIG. 8C illustrates thesegment of FIG. 8B in an expanded configuration. FIGS. 8D, 8E and 8F areplanar views of bioabsorbable stent scaffold walls showing alternatedesign embodiments of the connection elements which can be substitutedbetween meandering strut elements. FIG. 8G is a planar view of abioabsorbable stent scaffold wall showing an alternate design embodimentof the strut and hoop/ring patterns and how the design can be modifiedby alternate connection elements to change the flexibility of the stentscaffold. FIG. 8H illustrates a stent scaffold as manufacture whichshows the nested hoop/ring structure intercalated between meanderingstrut elements. FIG. 8I is FIG. 8H in a partially expandedconfiguration, and FIG. 8J is the same as 8H in an expandedconfiguration and FIG. 8K in a fully expanded configuration.

FIG. 9A depicts a planar view illustration of a biabsorbable stentscaffold showing the various components, nested hoop/ring structuralelements, meandering/sinusoidal strut components, end ring element andmodified connection structures having an o-ring like shape where theelements meet. FIG. 9B illustrates an oblique view of a stent structurescaffold as illustrated in FIG. 9A in an expanded configuration.

FIG. 10A illustrates the connection elements of a bioabsorbable scaffoldas described in FIG. 9A showing the state of the connections asmanufacture; FIGS. 10B and 10C in a partially expanded state and FIG.10D in a fully expanded state.

FIG. 11A depicts a planar view of an unexpanded alternate bioabsorbablestent scaffold design showing alternate pattern of connections betweenstrut elements and comprising end rings structures. FIG. 11B is FIG. 11Ain an expanded configuration. FIG. 11C illustrates a bioabsorbable stentstructure as illustrated in FIG. 11A mounted on a balloon catheter in anexpanded configuration.

FIG. 12A depicts a planar view of an alternate embodiment of abioabsorbable stent scaffold structure showing alternate design for thestrut elements in expanded configuration and hoop/ring elements. FIG.12B is a bioabsorbable stent structure of FIG. 12A in an expandedconfiguration and mounted on a balloon catheter.

FIG. 13A illustrates a bioabsorbable stent scaffold embodimentcomprising radio-opaque marker structures positioned at the end ring andthe connection elements between strut segments. FIG. 13B illustrates anembodiment wherein the radio-opaque material is position in a diagonalpattern for identification by radiography of the device afterimplantation.

FIG. 14A-14D illustrates alternate embodiments of isolated marker labelstructures of a bioabsorbable stent scaffold in cross-section.

FIGS. 15A and 15B further illustrate the position at which labelradio-opaque markers are placed in a bioabsorbable stent scaffoldembodiment and FIG. 15C is a radiography of a radio-opaque marker labelin a bioabsorbable stent strut embodiment.

FIG. 16A is an illustration of a planar view of an end of a stentembodiment comprising an end ring element, a locking mechanism and astent strut meandering element in an expanded configuration. FIG. 16B isFIG. 16A showing the stent scaffold in a crimped configuration. FIG. 16Cis an illustration of an the expanded stent scaffold showing the stressforce distribution. FIG. 16D illustrates a segment of a bioabsorbablestent scaffold embodiment showing nested hoop/ring structures, stentmeandering segments and locking mechanisms or retention features whichcan alternate in design for engagement.

FIGS. 17A and 17B depict alternate embodiments of a stent scaffold inexpanded planar view and showing disengaged locking mechanisms and endring structures at its ends.

FIGS. 18A-18F are illustrations of an alternate embodiment of abioabsorbable stent scaffold showing the locking mechanism at the endrings of the device in planar and oblique views as well as disengage andengage positions. FIG. 18G illustrates an embodiment wherein the stentscaffold is mounted on a balloon catheter and the locking mechanism areengage to retain the stent on the catheter in a uniform configuration inthe plane of the body of the stent. FIG. 18H is a frontal view of thestent scaffold of FIG. 18G showing the catheter as a circle, end ringand balloon.

FIG. 19A depicts a planar view of a stent scaffold embodiment showing analternate embodiment of the locking mechanism at the ends of the stentas manufactured. FIG. 19B depicts FIG. 19A in a crimped position showingan engaged locking mechanism. FIG. 19C shows an enlarged planar view ofthe locking mechanism in the crimped position, partially expandedconfiguration (FIG. 19D) and oblique views of the end rings with lockingmechanism partially engaged (FIG. 19E); crimped (FIG. 19F) and mountedin a balloon catheter (FIG. 19G).

FIG. 20A depicts an planar view of an alternate design locking mechanismof bioabsorbable stent embodiment in an expanded configuration; crimpedconfiguration (FIG. 20B). FIG. 20C is a planar view of an end segmentshowing a snap-fit locked end in a crimped configuration and expanded(FIG. 20D). FIGS. 20E and 20F represent oblique views of the stentscaffold of FIGS. 20A-20F in expanded and crimped configurations,respectively. FIG. 20G illustrates the stent scaffold mounted on aballoon catheter.

FIG. 21 depicts a photograph of a bioabsorbable stent scaffoldembodiment as manufactured being held between a person's thumb and indexfinger and showing the flexibility of the device.

DETAILED DESCRIPTION

Disclosed herein are novel structure elements, and novel compostionswhich may be used to make such novel structural elements. The presentembodiments may find use in the treatment of many diseases andphysiological ailments.

In recent years, metallic stents have come into use to aid in theclearing the clogged lumen of the vascular system. However, the efficacyof metallic stent implants in vascular arteries has been diminished bycertain disadvantageous results. For example, since such stents haveshown a tendency to stimulate formation of scar tissue or restenosis inthe wound inflicted in the vascular area of deployment. This effectbecomes more detrimental in the use of small diameter tubes in therapy.Moreover, it is important to avoid arterial wall damage during stentinsertion. These factors (although somewhat difficult to control in thefirst instance) are aimed at trying to reduce the mechanical reasonsthat lead to excessive clot and scar formation within the vessel lumen.

Stent structures typically comprise a number of meandering patterns. By“meandering” it is meant moving along a path that is other than strictlylinear. Due to the need to have an unexpanded form to allow for easyinsertion of a stent into its biological milieu, such as, withoutlimitation, the vasculature, the meandering patterns making up a stentare often sinusoidal in nature, that is having a repeating sequence ofpeaks and troughs. Often such sinusoidal structures are normalized suchthat each peak or trough is generally of the same distance as measuredfrom a median line. By “non-sinusoidal” it is meant a pattern not havinga repeating sequence of peaks and valleys, and not having a series ofraised portions of generally the same distance as measured from a medianline nor a series of depressed portions of generally the same distanceas measured from a median line. A stent may be characterized as havingthree distinct configurations, an unexpanded state (as manufactured), acrimped state (a compressed state as compared to the unexpanded state),and an expanded state (as deployed as an implant in vivo).

While the configurations disclosed herein are not limited to fabricationby any particular material, in certain embodiments such configurationsare constructed from a flexible, elastic, and bioabsorbable plasticscaffold. In embodiments disclosed herein, there is illustrated abioabsorbable and expandable scaffold of various shapes, patterns, anddetails fabricated from bioabsorbable polymers and polymer compositions.The scaffolds in an advantageous embodiment balance the properties ofelasticity, rigidity and flexibility while being more biocompatible,less thrombogenic and immunogenic than prior art polymeric medicaldevices. Such embodiments may provide means for preventing device creepor repositioning when crimpedly placed on a carrier as well as whenexpandedly placed in a living organ space. Stent implants may employ aballoon expandable medical device which comprises a thermal balloon ornon-thermal balloon.

Now turning to the figures, FIG. 1 is a computer simulation illustrationdepicting a partial view of an embodiment of a bioabsorbable medicaldevice in unexpanded form depicting scaffold strut segments 17, nestedhoop structures 14 and end rings 16, both comprising structures not inthe same plane, locking mechanism 18 connected to another lockingmechanism (not shown) and interconnection “H” regions 15 having an ringexpansion through-hole 11 at the nested hoop structures 14.

FIG. 2 is a computer generated illustration of an embodiment comprisinga bioabsorbable stent design in a nearly expanded configuration showingthe nested hoop structures 14 (or ring structures) and end rings 16 nowin generally in the same plane, meandering strut pattern 17 and lockingmechanism 18 detached from another locking mechansim. Expansionthrough-hole 11 as shown has been stretched into an oblong hole in suchexpanded configuration.

FIG. 3A depicts a computer simulation illustrating a prematurelyexpanded biabsorbable stent scaffold showing an alternating ring or hoopstructures with a meandering strut element pattern 17 and lockingmechanism 18. FIG. 3B is the same stent scaffold as in FIG. 3A showing aring segment in a different state of stress. In either case, thestructure comprising each ring or hoop is generally in the same plane.

FIG. 4A illustrates is a planar view of an embodiment showing a stentscaffold pattern 15, which may be bioabsorbable, in the shape of an Swhich can be replaced with other designs as shown. FIG. 4A also showsthe nested hoop/rings structures 14. FIG. 4B is an alternate embodimentin a planar configuration which illustrates the nested ring features 14,wherein the stent strut structure can be replaced with any of the designencompassed at 8. FIG. 4C is a planar view illustration of an unexpandedscaffold embodiment of the invention in which the structural sinuosiodalpattern 17 forms helical patterned structures 9 in the overall structure(shown as diagonal patterns in the planar view). FIG. 4D illustrates apartial unexpanded stent structure 16 formed of the scaffold of FIG. 4Cwith hoop or ring structural elements 14 and scaffolding elements in theform as manufactured. FIG. 4E illustrates the stent structure of FIG. 4Din a partially expanded configuration. FIG. 4E illustrates the stentstructure of FIG. 4D in an expanded configuration with reach ring as aitem in substantially the same plane.

FIG. 5 depicts an oblique view of an unexpanded bioabsorbable stentembodiment exhibiting meandering strut segments 22 in a sinusoidalpattern and end ring 23.

FIG. 6A depicts a partial top view of an expanded hoop or ring, whileFIG. 6B illustrates such hoop or ring when not expanded, shown in thedrawing as composed of meandering sinusoidal (6B) bioabsorbable strutelements of a stent embodiment. FIG. 6C illustrates a hoop or ringelement of a bioabsorbable stent showing how radial/transverse load isdistributed through a ring structure. As illustrated such structureprovides a better distribution of forces keeping such stent open underforces that might otherwise cause deformation of the stent.

FIG. 7A-7C illustrates the polymer fibers alignment in embodiments ofthe bioabsorbable medical devices and how the alignment undergoesplastic deformation upon stress. FIG. 7A illustrates the amorphous stateof the polymer composition for making the devices. FIG. 7B illustratesthe polymer fibers alignment in a partially expanded configuration andFIG. 7C illustrates the crystalline state of the fibers upon expansionof a bioabsorbable stent embodiment composed of racemate orstereocomplex polymeric compositions.

FIG. 8A illustrates a planar view of an unexpanded bioabsorbable stentscaffold embodiment comprising, structural meandering strut elements 17,nested hoop/ring elements 14 and having end rings 16 at the openings ofthe stent tube. FIG. 8B is a planar view of a section of the stentscaffold of FIG. 8A illustrating the structural meandering strutelements 17, nested hoop/ring elements 28, 30 and connection structureswhich form the stent scaffold. The stent scaffold is shown in a state asmanufactured and also shows the nested rings structures 28, 30 invarious configurations. Focusing on the connections between structuralmeandering elements and hoop elements there may be seen the shape of astylized letter H. FIG. 8C illustrates the segment of FIG. 8B in anexpanded configuration. FIGS. 8D, 8E and 8F are planar views ofbioabsorbable stent scaffold walls showing alternate design embodiments17 of the connection points between meandering strut elements 17 andring structures 15 (nested) and 16 (terminal ring structure). FIG. 8G isa planar view of a bioabsorbable stent scaffold wall showing analternate design embodiments of the strut and hoop/ring patterns and howthe design can be modifies by alternate connection elements to changethe flexibility of the stent scaffold. FIG. 8H illustrates a stentscaffold as manufacture which shows the nested hoop/ring structureintercalated between meandering strut elements. FIG. 8I is FIG. 8H in apartially expanded configuration, and FIG. 8J is the same as 8H in anexpanded configuration and FIG. 8K in a fully expanded configuration.

FIG. 9A depicts a planar view illustration of a biabsorbable stentscaffold showing the various components, nested hoop/ring structuralelements 28, meandering/sinusoidal strut components 38, end ringelements 16 and modified connection structures 6 having an o-ring likeshape where the elements meet. FIG. 9B illustrates an oblique view of astent structure scaffold as illustrated in FIG. 9A in an expandedconfiguration.

FIG. 10A illustrates the connection structures 6 of a bioabsorbablescaffold as described in FIG. 9A showing the state of the connections asmanufactured; FIGS. 10B and 10C in a partially expanded state and FIG.10D in a fully expanded state. As illustrated the through-void shapechanges as the scaffold is expanded.

FIG. 11A depicts a planar view of an unexpanded alternate bioabsorbablestent scaffold design showing alternate pattern of connections betweenstrut elements and comprising end rings structures. FIG. 11B is FIG. 11Ain an expanded configuration. FIG. 11C shows the same in expanded statedeployed on a expanded balloon catheter.

FIG. 12A depicts a planar view of an alternate embodiment of abioabsorbable stent scaffold structure showing alternate design for thestrut elements in expanded configuration including hoop/ring elements 14and 16. FIG. 12B may be a bioabsorbable stent structure of FIG. 12A inan expanded configuration and mounted on a balloon catheter.

FIG. 13A illustrates a bioabsorbable stent scaffold embodimentcomprising radio-opaque marker structures 65 positioned at the end ringand the connection elements between strut segments. FIG. 13B illustratesan embodiment wherein the radio-opaque material is position in adiagonal pattern 65′ for identification by radiography of the deviceafter implantation.

FIG. 14A-14D illustrates alternate embodiments of isolated marker labelstructures of a bioabsorbable stent scaffold in cross-section. Asillustrated the isolated marker may be placed on the stent (14D), or ina recess (14B) or in a variety of through-boles (14A and 14C).

FIGS. 15A and 15B further illustrate the position at which labelradio-opaque markers 65 are placed in a bioabsorbable stent scaffoldembodiment. FIG. 15C is a close-radiograph of a radio-opaque markerlabel in a bioabsorbable stent strut embodiment.

FIG. 16A is an illustration of a planar view of an end of a stentembodiment comprising an end ring element 16, a locking mechanism 75 anda stent strut meandering element 17 in an expanded configuration. FIG.6B is FIG. 16A showing the stent scaffold in a crimped configurationwith interlocking locking mechanisms 75. FIG. 16C is an illustration ofan the expanded stent scaffold showing the stress force distribution,and showing the decoupling of locking mechanisms 75 when in the stent isin an expanded configuration. FIG. 16D illustrates a segment of abioabsorbable stent scaffold embodiment showing nested hoop/ringstructures 14, stent meandering segments 17 and locking mechanisms 11 orretention features which can alternate in design for engagement.

FIGS. 17A and 17B depict alternate embodiments of a stent scaffold inexpanded planar view and showing disengage locking mechanisms 75 and endring structures 16 at its ends. As shown mechanisms 75 are snap-fitconnections with male-female portions.

FIGS. 18A-18F are illustrations of an alternate embodiment of abioabsorbable stent scaffold showing the locking mechanism 75 at the endrings of the device in planar and oblique views as well as disengage andengage positions. Locking mechanism 75 in such embodiment comprises asnap-fit ball joint. FIGS. 18A, 18D and 18E show disconnected lockingmechanism 75. FIGS. 18B, 18C and 18F show the locking mechanism 75 inlocked state. FIG. 18G illustrates an embodiment wherein the a stentscaffold is mounted on a balloon catheter 60 and the locking mechanismare engaged to retain the stent on the catheter in a uniformconfiguration in the plane of the body of the stent. FIG. 18H is afrontal view of the stent scaffold 16 of FIG. 18G showing the catheteras a circle 60, end ring 16 and balloon 70.

FIG. 19A depicts a planar view of a stent scaffold embodiment showing analternate embodiment of the locking mechanism 80 at the ends of thestent as manufactured. FIG. 19B depicts FIG. 19A in a crimped positionshowing an engaged locking mechanism 80. FIG. 19C shows an enlargedplanar view of the locking mechanism in the crimped position, while FIG.19D shows unlocking in a partially expanded configuration. FIGS. 19E and19F shows oblique views of the end rings with locking mechanism 80partially engaged (FIG. 19E); crimped (FIG. 19F) and mounted in aballoon catheter (FIG. 19G).

FIG. 20A depicts an planar view of an alternate design locking mechanismof bioabsorbable stent embodiment in an expanded configuration. FIG. 20Bdepicts the same planar view in a crimped configuration. FIG. 20C is aplanar view of an end segment showing a snap-fit locked end in a crimpedconfiguration. FIG. 20D shows the end segment of FIG. 20C when expandedto cause unlocking of locking mechanism 80. FIGS. 20E and 20F representoblique views of the stent scaffold of FIG. 20C in expandedconfiguration (FIG. 20E) with unlocked locking mechanism 90 and crimpedconfiguration (FIG. 20F), with locked locking mechanism 90,respectively. FIG. 20G illustrates the stent scaffold of FIGS. 20A-20Fmounted on a balloon catheter.

FIG. 21 depicts a photograph of a bioabsorbable stent scaffoldembodiment as manufactured being held between a person's thumb and indexfinger and showing the flexibility of the device. As can be seenconsiderable flexibility may exist.

Polymer implant embodiments may be nearly undetectable due to lack ofmass density or absence of signal. Therefore, such embodiments mayincorporate a radio opaque marker, such a radio opaque dots. Such dotsmay be produced by applying radiopaque material in paste form intorivet-like depressions or receptacles in or on the scaffold strutelements. As shown, regular patterns of radiopaque dot deposits on thescaffold would advantageously aid in the ease of radiological detectionof such implant location.

In one scaffold embodiment, the scaffold comprises a crimpable polymericstent, which can be inserted by means of a balloon delivery system forvascular implantation. However, the flexible plasticity of the stentscaffold can lead to relaxation of the crimped configuration on thecarrier system used for vascular insertion or delivery. Consequently,the crimped scaffold acquires the tendency to “creep” that move off theintended location of the balloon carrier or come loose entirely.Therefore, in preferred embodiments, the polymeric device such as astent is provided with a safety mechanism for guarding againstaccidental opening of the scaffold while being mounted or loaded onto adelivery system and during deployment of the crimped device to a desiredlocation within the tubular organ. Multiple safety mechanism aredisclosed herein which can be used with a medical device. The securingmechanisms can be designed adjacent to the circumferential distal andproximal end ring struts (secondary meandering strut elements). Inspecific embodiments, the scaffold has now been furnished with lockingmeans to keep the crimped structure in a securely clamped position toprevent buckling and for secure deployment of the device. In addition,the locking means can prevent a loosening of the crimped configurationof the plastic scaffold from the carrier system during handling. Thelocking mechanism is affected by structurally interfering design and/orby added frictional properties which may be activated by mutual pressureengagement. According to an embodiment, frictional aspects of thelocking mechanism may be affected by selectively modified plasticcompositions, wherein ionic or non-ionic additive substances maycontribute to secure the crimped configuration of a scaffold.

In specific embodiments, the scaffold employs various designs includingsnap-fit features at or near the distal and proximal end to lock thescaffold in the crimped position on the carrier portion of the deliverysystem. In this and other embodiments, one or more snap-fit structurescan be designed, positioned at the end meandering strut element of ascaffold structure or alternatively also in certain repeat positionswithin scaffold structure. As intended in the crimped configuration, thelocking mechanism increases stent retention force. Adjacent snap-fitlocking features are designed to be continuous or attached to or part ofa secondary meandering or ring/hoop structure, and are operativelyconfigured to engage and lock-down the ends of the scaffold device inthe crimped position to afford a sufficient retentive force for holdingthe scaffold in place along the longitudinal axis of the device andmaintain uniformity of its diameter. In certain embodiments, and uponexpansion of the device, the end meandering element may form acompletely straightened ring for added hoop strength of, for example, astent.

As described above, the device may be provided with a structural lockingmeans in the form of key-in-lock configuration members, wherein thedesign resembles a snap-fit ball-socket joint type interlocking means,in one embodiment, there is provided one or more nested elementalmeandering structures for forming loops or ring-like patterns in anexpanded configuration.

The scaffold embodiment may be configured in number of ways. Forexample, one may use end ring type locking positions in the form of asnap-fit where a cantilever shape or finger strut element fits tightlyover an adjacent counterpressuring strut surface when locked down in thecrimped configuration of the stent. Locking means comprise in anotherembodiment, a finger-like cantilever extension that engagingly slides ina snap-fit manner over a commensurately curved surface portion of theadjacent piece of the plastic scaffold strut element. In thisembodiment, the securing mechanism works as a break or friction devicewhich creates sufficient friction to keep the scaffold end in thecrimped-down position. An alternative locking means is illustrated inlocked form of a ball-joint snap-fit locking means.

Another alternative mechanism is a snap-fit locking device wherein thecantilever embodiment utilizes a notch style receptacle form on anadjacent strut element to receive the tip portion of the cantilever.

In one embodiment, the structural locking means of the medical devicecan be designed in key-in-lock or ball-joint configuration wherein theoppositely oriented cantilever hook-type interlocking Means in a lockedand unlocked position.

In another embodiment, the medical device can be provided withstructural locking means configured in a key-in-lock configurationwherein the design resembles a snap-fit dovetail type interlockingmeans.

The locking means can be provided in the form of snap-fit features nearor at one or both end portions of the scaffold entity so that it mayremain in place on the carrier means during delivery to the treatmenttarget area until or unless the expanding carrier system is activated todisengage the device during deployment at implantation. Duringdeployment, the locking mechanism can disengage from one anotheruniformly. In one embodiment, the locking mechanism can be fullystretched so that the connecting stabilizer rings at one or both ends ofthe longitudinally meandering scaffold members after implantation into,for example, the luminal wall of a blood vessel or other target area.

In one embodiment structure, meandering struts alternate with eachother. Both primary meandering struts and secondary meandering orringlet strut elements are held in position with respect to each otherin the crimped configuration as well as the expanded or implantedconfiguration by means of special connectors of various shapes locatedat crossing points between adjacent struts. Each such crossing connectoror a select number thereof may be used in a repeat pattern. Theseconnecting elements are capable of keeping the meandering struts of thescaffold embodiment in a regularly spaced position. These connectors areintended to withstand the change from the initial tube confirmation to atightly crimped position on a delivery bulb/inserting device to astretchedly expanded configuration. The stretching of such a stentscaffold stresses and crystallizes the component struts and hoops/ringsinto circularity concomitant with the overall cylindrical or cone-likeshape. The strut connecting elements or connectors may be arranged inrepeat patterns to stabilize and connect adjacent meandering strutelements. This design is intended to keep the elastic flexiblemeandering struts located within the tube-like scaffold conformation.

In another embodiment, there is provided a cooling means or conditionfor immobilizing and stabilizing a plastic scaffold on the carriersystem in a crimped and locked down configuration for increasingreliability of the delivery system.

In another embodiment, the medical device comprises a polymeric scaffoldstructure which can orient and/or crystallize upon strain of deployment,for example during balloon dilation, in order to improve its mechanicalproperties. These mechanical properties include but are not limited toresistance to compression, recoiling, elastic

In another embodiment, the medical device produced from polymers orpolymeric compositions which upon breakdown in vivo, the polymerbyproducts resulting from such breakdown comprise “friendly” orbiocompatible compounds that have very low or substantially noimmunogenicity to the host, for example, and no significant granulationtissue can be stimulated to develop in the vascular wall.

In yet another embodiment, the medical device comprises polymers havingslow breakdown kinetics which avoid tissue overload or otherinflammatory responses at the site of implantation.

In one embodiment, a medical device may have a minimum of 30-dayretention in situ of clinically sufficient strength against creep, orbreak-up, and induces endothelialization after implantation.

An exemplary medical device can be structurally configured to providethe ability to change and conform to the area of implantation and toallow for the normal reestablishment of local tissues. For example, themedical device can transition from a solid polymer state to a “rubberystate” and allows for easier surgical intervention, than, for example,metal stents such as a stainless steel stent. The higher the deformedstate, the higher strength that is imparted to the device structuralcomponent.

In certain embodiments, the polymer composition can comprise a basepolymer which can be present from about 70% to 95% by weight, or fromabout 70% to 80% by weight of the composition.

In one embodiment, the polymer formulation can comprise from about 70%by weight poly L-lactide (about 2.5 to 3 IV) with the polyL-lactide-co-TMC(70/30 w/w) (1.4 to 1.0 IV).

In another embodiment, the polymer formulation comprises 70% by weighttriblock poly L-lactide-co-PEG(99/01) (2.5 to 3 IV) with the polyL-lactide-co-TMC(70/30) (1.4 to 1.6 IV).

In one embodiment, the polymer composition can also comprise aformulation of about 70% by weight diblock polyL-lactide-co-PEG-MME(95/05) (2.5 to 3 IV) with polyL-lactide-co-TMC(70/30 w/w) (1.4 to 1.6 IV).

An embodiment of the biodegradable medical device comprises a basepolymer comprising, for example ply L-Lactide or poly D-Lactide, amodifying co-polymer, such as poly L(or D)lactide-co-Tri-methylene-carbonate or poly L(orD)-lactide-co-e-caprolactone as described above.

Polymerization preferably proceeds by block polymerization of D and Lisomeric forms so as to achieve a polymeric racemate moiety thatenhances the transition from generally amorphous configuration to aexpansion related stretch or strain induced crystalline realignment ofthe polymeric moiety. The mechanical properties concomitantly changefrom crimpable flexibility to hoop extended rigidity, most particularlythe latter change occurring in the expansion of nested andend-positioned rings or hoops from secondary meandering struts.

In one embodiment, pharmaceutical compositions can be incorporate withthe polymers by, for example, admixing the composition with the polymersprior to extruding the device, or grafting the compositions onto thepolymer active sites, or coating the composition onto the device.

The medical device can comprise any polymeric medical device forimplantation including stents, grafts, stent grafts, synthetic vasculargrafts, shunts, catheters, and the like.

An exemplary medical device may be a stent, which is structurallyconfigured with a first meandering/sinusoidal elements and having anumber of nested second element that when expanded comprises ring-likestructural elements. The stent may also comprise snap-fit structures foraiding in crimping and for maintaining the crimped state for deployinginto, for example, an artery or a vein, and be able to expand in situ,and conform to the blood vessel lumen to reestablish blood vesselcontinuity at the site of injury. In alternate embodiments, the stentmay be configured to have many different arrangements, patterns ordesigns so that it is crimpable when loading and expandable and flexiblebut compression-resistant or resilient at physiological conditions oncedeployed. Moreover, the expanded implant may display mechanicalproperties such as a degree of rigidity and concomitant flexibilitypreventing dislocation or creep.

Various embodiments of biodegradable polymeric stents, and/or stentwalls with different configurations. For example, the stent is a tubularstructure comprising a scaffold wherein the strut elements are designedto allow blood to traverse through open spaces between the elements. Inparticular the meandering struts are spaced so that most of the adjacenttissue surface remains available for contact with blood. The particularstent design features include different radial and longitudinalparameters depending on the size of the stent to be deployed. A stentconfiguration can be varied such as bifurcated or configured to allowfor further deployment to other vessels distal to the site of initialimplantation.

A stent can contain a uniform and flexible scaffolding modified withside-branches. Accordingly, after initial deployment of the stent insitu, a second stent can be inserted through the luminal walls of thefirst stent.

In an embodiment, the medical device can be modified to include aradio-opaque, or radiolucent material for detecting its location afterdeployment or to ascertain the effects of long-term use (6 months or 2years). There are different types of modifications available, such ase.g. diffuse or spot marking of the scaffold. Accordingly theradio-opaque materials can be incorporated directly in the initialplastic composition either as an admixture or covalently boundcomponent. Alternatively, the radio-opaque material can be placed in aplurality of specific spot receptacles regularly distributed on or inthe scaffold. Or the radio-opaque or radiolucent materials can byapplied as part of a thin coating on the scaffold.

Therefore, the contrast detection enhancement of tissue implants byelectron-dense or x-ray refractile markers is advantageous. Such markerscan be found in biodegradable spot depots filled with radiopaquecompositions prepared from materials known to refract x-radiation so asto become visible in photographic images. Suitable materials includewithout limit, 10-90% of radiopaque compounds or microparticles whichcan be embedded in biodegradable moieties, particularly in the form ofpaste like compositions deposited in a plurality of cup shapedreceptacles located in preformed polymeric scaffold strut elements.

The radiopaque compounds can be selected from x-radiation dense orrefractile compounds such as metal particles or salts. Suitable markermetals may include iron, gold, colloidal silver, zinc, magnesium, eitherin pure form or as organic compounds. Other radiopaque material istantalum, tungsten, platinum/iridium, or platinum. The radiopaque markermay be constituted with a binding agent of one or more aforementionedbiodegradable polymer, such as PLLA, PDLA, PLGA, PEG, etc. To achieveproper blend of marker material a solvent system is includes two or moreacetone, toluene, methylbenzene, DMSO, etc. In addition, the markerdepot can be utilized for an anti-inflammatory drug selected fromfamilies such as PPAR agonists, steroids, mTOR inhibitors, Calcineurininhibitors, etc. In one embodiment comprising a radioopaque marker, ironcontaining compounds or iron encapsulating particles are cross-linkedwith a PLA polymer matrix to produce a pasty substance which can beinjected or otherwise deposited in the suitably hollow receptaclecontained in the polymeric strut element. Such cup-like receptacles aredimensioned to within the width of a scaffold strut element. Heavy metaland heavy earth elements are useful in variety of compounds such asferrous salts, organic iodine substances, bismuth or barium salts, etc.Further embodiments can utilize natural encapsulated iron particles suchas ferritin that may be further cross-linked by cross-linking agents.Furthermore, ferritin gel can be constituted by cross-linking with lowconcentrations (0.1-2%) of glutaraldehyde. The radioopaque marker may beapplied and held in association with the polymer in a number of manners.For example, the fluid or paste mixture of the marker may be filled in asyringe and slowly injected into a preformed cavity or cup-likedepression in a biodegradable stent strut through as needle tip. Thesolvents contained in the fluid mixture can bond the marker material tothe cavity walls. The stent containing radiopaque marker dots can bedried under under heat/vacuo. After implantation, the biodegradablebinding agent can breakdown to simple molecules which areabsorbed/discharged by the body. Thus the radiopaque material willbecome dispersed in a region near where first implanted.

The scaffold mechanical properties are time tested in situ for anyretention of recoil and the presence of restenotic tissue. Similarly,scaffold polymer biodegradation and metabolism may be assessed byquantitative change measurement in echogenicity and tissue composition.Regional mechanical properties may be assessed by palpography (6 months;2 years). Mass reduction over time of polymer degradation may beassessed by OCT (6 months; 2 years). Binary restenosis may bequantitatively measured with MSCT(18 m). The experimental evidencesupports the advantages of the biodegradable and absorbable scaffold asused for example in a stent. It has been found that the scaffoldperforms like a metallic drug eluting stent (DES) in terms of acutedelivery and conformity. However, it has been found that the emplacedscaffold is naturally absorbed and fully metabolized. Therefore, thebioabsorbable scaffold, which may be in the form of a tube shaped stent,is metabolized completely leaving no permanent implant and leaves behinda healed natural vessel or tissue. The scaffold of this invention iscompatible with CT imaging.

A process for making an exemplary medical device comprises: preparing asuitable polymer composition with or without one or more pharmaceuticalsubstances; molding or extruding the polymer composition to configurestructurally the device for implantation. In the case of a stent, a tubeshaped structure is formed and it is subsequently cut with, for example,the aid of a laser to form desired patterns.

In one embodiment, a method for fabricating the medical device comprisespreparing a biodegradable polymeric structure; designing said polymericstructure to be configured to allow for implantation into a patient;laser cutting said structure into patterns configured to permittraversing of the device through openings and to allow for crimping ofthe device. Preferably, the patterned structure contains theaforementioned locking means for stabilizing the crimped device so as toretain it securely on the carrier/implant system.

In another embodiment, closure means of locking devices for aiding incrimping and loading a scaffold configuration may be further chemicallymodified or enhanced by adding biocompatible non-ionic or ionic agentsto the scaffold or scaffold composition or in the form of layers orgrafts. These modified anionic, cationic or nonionic layers can beuniform or minutely stippled onto the interlocking surfaces. The dosagelevels of the cationic or anionic agents which may also be surfactantsmay range from 0.01-10% by weight. External application of such ionicagents is preferred for easy soluble removal after expansion in situ.Low dosage levels of non-ionic agents are suitable for enhancingfrictional interaction particularly between parts of locking mechanism.Preferred are nonionic agents which may be FDA approved at dosage levelsranging from 0.05-2.5%. An embodiment for the friction-enhancedscaffold, or particularly, the interacting lock surfaces, providesnon-ionic doping of the modified layers. Suitable nonionic agents may beselected from chemicals such as ethoxylated fatty amines, fatty acidesters, and mono- and diglycerides.

While the invention has been particularly shown and described withreference to particular embodiments, it will be appreciated thatvariations of the above-disclosed and other features and functions, oralternatives thereof, may be desirably combined into many otherdifferent systems or applications. Also that various presentlyunforeseen or unanticipated alternatives, modifications, variations orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

1. An expandable biodegradable tubular scaffold comprising: a pluralityof biodegradable first meanders forming an interconnected mesh, saidmesh extending circumferentially about a longitudinal axis; wherein eachof said biodegradable first meanders are manufactured from a racemicpolymer which crystallizes under the strain of expansion of said tubularscaffold; and a plurality of biodegradable second meanders, each of saidsecond meanders being separate from another, and each extendingcircumferentially about said longitudinal axis in a single plane, saidsecond meanders being nest in, and interconnected to, said firstmeanders.
 2. The scaffold of claim 1 wherein said first meanders aregenerally parallel to said longitudinal axis.
 3. The scaffold of claim 1wherein said first meanders are generally diagonal to said longitudinalaxis.
 4. The scaffold of claim 1 wherein said first meanders aregenerally orthogonal to said longitudinal axis.
 5. The scaffold of claim1 wherein said first meanders are concentric about said longitudinalaxis.
 6. The scaffold of claim 1 wherein said second meanders are madeof a material which crystallizes when said tube is in its expandedstate, but does not substantially crystallize in its unexpanded state.7. The scaffold of claim 1 wherein at least one of said second meandersincludes at least one through-void.
 8. The scaffold of claim 7 whereinsaid at least one second member through-void is configured to permitstretching of said second member without failure of the member.
 9. Thescaffold of claim 1 wherein said first meanders form a strut patternthat is sinusoidal when said tube is in an expanded form.
 10. Thescaffold of claim 9 wherein said second meanders from a strut patternthat is substantially non-sinusoidal when said tube is in an expandedform.
 11. The scaffold of claim 1 wherein said first meanders form astrut pattern that extends from said proximal open end to said distalopen end of said tube.
 12. The scaffold of claim 11 wherein said secondmeanders form a strut pattern that is found at said proximal open endand said distal open end.
 13. The scaffold of claim 12 wherein saidsecond meanders form a strut pattern that is further found between saidproximal open end and said distal open end.
 14. The scaffold of claim 11wherein said second meanders form a pattern that is found between saidproximal open end and said distal open end but not at the proximal openend or said distal open end.
 15. A method for fabricating a tube-shapedscaffold comprising: preparing a racemic poly-lactide mixture;fabricating a biodegradable polymer tube of said racemic poly-lactidemixture; laser cutting said tube until such scaffold is formed.
 16. Amethod as in claim 15 wherein said fabrication is by a moldingtechnique.
 17. A method as in claim 15 wherein said fabrication is by anextrusion technique.
 18. A method as in claim 16 wherein said moldingtechnique is substantially solvent-free.
 19. A method as in claim 16wherein said extrusion technique is substantially solvent-free.
 20. Amethod for fabricating the tube-shaped scaffold comprising: blending apolymer composition comprising a crystallizable composition comprising abase polymer of poly L-lactide or poly D-lactide linked with modifyingcopolymers comprising poly L(or D)-lactide-co-tri-methylene-carbonate orpoly L(or D)-lactide-co-e-caprolactone in the form of block copolymersor as blocky random copolymers wherein the lactide chain length issufficiently long enough to allow cross-moiety crystallization; moldingsaid polymer composition to structurally configure said scaffold; andcutting said scaffold to form the desired scaffold patterns.
 21. Themethod of claim 20 wherein said blended composition comprises a recemicmisture of poly L-lactide and poly-D lactide.
 22. A stent consistingessentially of a racemic mixture of a poly-L and poly-D lactide.
 23. Astent of claim 22 further comprising trimethylcarbonate.
 24. A stent ofclaim 23 wherein the trimethylcarbonate does not comprise more than 40%of of the weight of the stent.